The present invention relates to an improved optical fiber cable. More particularly, the invention relates to an optical fiber cable in which water is prevented from penetrating the fibers of the cable.
Although technical advances have come quickly in the art of optical fiber cables, such cables still often suffer an important drawback, namely, a deterioration of transmission characteristics due to penetration of water into the fibers of the cable. (This problem occurs too of course in electrical conductor type cables.)
In order to overcome this problem, it has been the practice to periodically pass dry air through the cables after they have been installed. Doing so, however, is expensive. Moreover, access to buried cables is often quite difficult.
Another approach has been to cover the fibers with a water-blocking compound such as has been used in electrical conductor cables. Such a compound, however, must be applied uniformly if it is to be fully effective. This proves difficult to accomplish in practice. A high degree of skill is required and it is necessary to provide a cushioning fabric for protecting the fibers and a grooved spacer or a tube to hold the fibers. Further, filling of the cable with the water-blocking compound while laying a cable is difficult and the compound itself can foul the work area if not handled properly. The compound, because it is quite viscous, cannot easily be removed from the cable. This makes the cable very difficult to splice.